Measurement of water flow rates in large diameter pipes has been the subject of inventive and innovative efforts for some time, particularly in respect to achieving economics in the measurement device, low head loss across the device, and accuracy of measurement. Diverting the flow of some water from the main flow within the primary conduit into a smaller diameter measuring shunt has been disclosed in U.S. Pat. Nos. 793,486, 1,954,386, and 3,314,290 and the references cited therein, in addition to other publications. In spite of the advances made in water flow measurement by these disclosures, the problems of cost and accuracy still persist.
It is therefore an object of the present invention to provide a venturi type of shunt flow meter which is accurate, has low manufacturing cost, and can be easily installed in an existing or new pipe line.
A further object of the invention is to provide means in the by-pass line to enhance the ability of that line to accomodate a fluid flow which will remain porportional to h (where "h" is the pressure differential between the inlet and outlet of the shunt line, created by the venturi), therby stabilizing the ratio throughout the low-to-high flow rate range.
Another object of the invention is to provide means in a shunt flow meter to convert head loss in the shunt loop from a wall-friction controlled system to a fluid-eddy controlled system by introducing a small orifice in the shunt line.
Still another object of the invention is to stabilize the ratio between the main flow and the shunt flow with respect to time in order that the ratio remain constant from low to high flow rates.
Other and further objects, features and advantages of the invention will be apparent from a reading of the following detailed description of the preferred form of the invention taken in connection with the accompanying drawings.